1. Field of the Invention
The present invention relates to a deposition apparatus. More particularly, the present invention relates to a deposition apparatus for preventing undesired deposition on the back side of a substrate.
2. Description of the Related Art
In manufacturing semiconductor devices, various apparatuses and processes have been developed to provide a high quality thin film on a substrate. Several methods have been used to form a thin film, employing surface reaction of a semiconductor substrate. The methods include vacuum evaporation deposition, Molecular Beam Epitaxy (MBE), different variants of Chemical Vapor Deposition (CVD) (including low-pressure and organometallic CVD and plasma-enhanced CVD), and Atomic Layer Epitaxy (ALE). ALE was studied extensively for semiconductor deposition and electroluminescent display applications, and has been more recently referred to as Atomic Layer Deposition (ALD) for the deposition of a variety of materials.
In deposition apparatuses, it is desirable to prevent reactants from being deposited at an undesired portion of a substrate. For example, if reactant gases enter a space between a substrate and a substrate support in a reaction chamber, an undesired film or impurity particles may be deposited on a back side of the substrate. Such an undesired film or impurity particles may contaminate the reaction chamber, adversely affecting the quality of a thin film deposited on the substrate and the productivity of the deposition apparatus. Thus, there is a need for preventing formation of such an undesired film or impurity particles. Particularly, there is a need for preventing such problems when depositing a metal, such as copper (Cu), ruthenium (Ru), platinum (Pt), or the like.
For preventing the formation of an undesired film or impurity particles, a conventional deposition apparatus includes a gas blocking member that blocks edges of a substrate, such that the edges of the substrate are not exposed to reactant gases. FIG. 1 is a schematic cross-sectional view of a conventional deposition apparatus 100 disclosed in U.S. Pat. No. 7,138,336, the disclosure of which is incorporated by reference. Referring to FIG. 1, the deposition apparatus 100 includes a substrate support 160 and a reactor wall 122 forming a reactor chamber. The reactor wall 122 is surrounded by a heater 204. A substrate 156 is mounted on the substrate support 160 during a deposition process.
The deposition apparatus 100 also includes a gas inflow tube 110, a gas outlet tube 118, a plasma generation barrier 128, a showerhead assembly 130, a showerhead insulating wall 138, an inert gas passage 148, a gas sealer ring 158, a substrate support 160, a radio frequency (RF) connecting terminal 166, an insulation tube 168, a vacuum pump 198, and a reactor body 200. The deposition apparatus 100 further includes a girding plate 178, drive shafts 180, pneumatic cylinders 184, an inert gas inlet tube 190, and an inert gas outlet tube 192. The reactor body 200 is connected to ground 194.
The gas inflow tube 110 serves as a conduit for supplying a plurality of reactant gases into the reaction chamber. The gas inflow tube 110 is positioned in the upper part of the reactor wall 122.
The showerhead assembly 130 is positioned inside the reactor wall 122, defining a reaction space 154 together with the substrate support 160. The illustrated showerhead assembly 130 includes a volume adjusting horn 140 and a showerhead plate 142. The volume adjusting horn 140 and the showerhead plate 142 may be formed of a conductive material, such as a metal. The volume adjusting horn 140 is in fluid communication with the gas inflow tube 110. The volume adjusting horn 140 provides gases from the gas inflow tube 110 to the showerhead plate 142. The showerhead plate 142 includes a plurality of gas dispersion holes for distributing the gases into the reaction space 154. The showerhead assembly 130 may be electrically connected to the radio frequency (RF) connection terminal 166. The showerhead insulating wall 138 covers side and top portions of the showerhead assembly 130 to electrically insulate the showerhead assembly 130.
The radio frequency connecting terminal 166 serves to receive radio frequency (RF) power from an external power source. The radio frequency connecting terminal 166 may include an inner tube 164 formed of a conductive material. The inner tube 164 is formed through the reactor body 200, the reactor wall 122, the plasma generation barrier 128, and the showerhead insulation wall 138, and electrically contacts the volume adjusting horn 140. The inner tube 164 is electrically connected to both the volume adjusting horn 140 and the showerhead plate 142, providing a positive (+) polarity to them.
The insulation tube 168, which is formed of an insulating material, surrounds the inner tube 164. The insulating tube 168 electrically insulates the inner tube 164 from the reactor body 200, the reactor wall 122, and the plasma generation barrier wall 128, which may be formed of a conductive material. The insulation tube 168 does not include a portion interposed between the inner tube 164 and the showerhead insulating wall 138 because the showerhead insulating wall 138 is formed of an insulating material. The plasma generation barrier wall 128 is interposed between the showerhead insulation wall 138 and the reactor wall 122 in order to prevent an electrical short through the showerhead assembly 130.
The gas sealer ring 158 is located on the top surface of a periphery of the substrate support 160. The gas sealer ring 158 includes a portion that contacts the bottom surface of the reactor wall 152. The gas sealer ring 158 is in a form of a thin flat washer with a beveled inner side and a square-edged outer side, and seals a gap between the substrate support 160 and the reactor wall 122. The gas sealer ring 158 may be formed of a material having a relatively low thermal expansion coefficient at a process temperature. For example, the gas sealer ring 158 may be formed of a ceramic material having excellent heat resistance. The gas sealer ring 158 may cover a top surface of the periphery of the substrate support 160. This gas sealer ring 158 prevents reactant gases from leaking, and protects the substrate support 160 from being exposed to the reactant gases. The gas sealer ring 158 will be described below in more detail with reference to FIG. 2.
For a deposition process, the substrate 156 is loaded onto the substrate support 160 in the deposition apparatus 100. The reaction chamber is defined by contacting the reactor wall 122 with the substrate support 160. The gas sealer ring 158 contacts and covers the edges of the substrate 156. The gas sealer ring 158 prevents the edges of the substrate 156 from being exposed to reactant gases such that the reactant gases do not flow to the back side of the substrate through the reactor wall 122 and the substrate support 160. Accordingly, substantially no undesired film and impurity particles may be formed on the back side of the substrate 156.
During the deposition process, an inert gas, such as argon (Ar), is supplied through the inner tube 164 of the radio frequency connection terminal 166. Then, the inert gas continues to flow through the inert gas passage 148 between the showerhead insulation wall 138 and the plasma generation barrier wall 128. The inert gas turns around the end part 148a of the inert gas passage 148, and joins the exhaust flow through a gap between the plasma generation barrier wall 128 and the reactor wall 122, and then eventually through the gas outlet tube 118. The inert gas is then exhausted through the vacuum pump 198. In certain instances, the inert gas may be supplied continuously during a deposition process. Such a continuous supply of the inert gas may block the exposure of the top and side portions of the showerhead insulation wall 138 to reactant gases, thereby preventing undesired deposition of a reactant material on the surface of the showerhead insulation wall 138.
Referring to FIG. 2, the deposition apparatus includes the gas sealer ring 158 covering peripheral portions of the substrate 156. The gas sealer ring 158 has a planar ring shape partially overlying the peripheral portions of the substrate 156. However, because the gas sealer ring 158 contacts the substrate 156 during processing, a heat loss may occur through the peripheral portions of the substrate 156 which the gas sealer ring 158 contacts. Accordingly, temperature distribution across the substrate 156 may be non-uniform, adversely affecting the uniformity of a thin film deposited on the substrate 156.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form prior art already known in this country to a person of ordinary skill in the art.